The invention relates to a non-magnetic metal sorting method and apparatus using a shifting magnetic field to select non-magnetic metals from a mixture including them.
A shifting electromagnetic field has been utilized to separate and select non-magnetic metals from a mixture having its iron component removed by means of magnets for the purpose of resource recovery from solid waste. For this purpose, there have been proposed in the art several apparatuses schematically shown in FIGS. 1 through 3. One example is shown in FIG. 1 in which a shifting electromagnetic field generator is utilized to produce an electromagnetic force acting in the direction indicated by the arrow a on the mixture including non-magnetic metal particles supplied from a chute 1 and transported by means of a belt conveyer 2 so that the non-magnetic metal particles are moved in the direction indicated by the arrow b and the remainder of the mixture is moved in the direction indicated by the arrow c. The apparatus shown in FIG. 2 includes a shifting electromagnetic field generator 3 to produce an electromagentic force in the direction indicated by the arrow a so that the non-magnetic metal particles are accelerated in the same direction as the direction of travel of the belt conveyer 2 and discharged in a position far away from the belt conveyer 2 as indicated by the arrow b while the remainder of the mixture is discharged in a position near the belt conveyer 2 as indicated by the arrow c. In the FIG. 3 apparatuses, a shifting electromagnetic field generator 3 is used to produce an electromagnetic force exerted in a direction opposite to the direction of travel of the belt conveyer 2 so that the non-magnetic metal particles are discharged as shown by the arrow b and the remainder of the mixture is discharged as shown by the arrow c.
Such conventional non-magnetic metal separating apparatus generally provide a satisfactory separation of non-magnetic metal particles from the mixture, but where the non-magnetic metal particles have different size from the remainder of the mixture, the conventional apparatus do not perform well. Where the size of the non-magnetic metal particles is relatively smaller than that of the remainder, the non-magnetic metal particles will be held between the larger particles of the remainder and cannot be effectively separated therefrom by the electromagnetic force acting on the non-magnetic metal particles. On the contrary, where the size of the non-magnetic metal particles is relatively larger than that of the remainder, the non-magnetic metal particles will trap the smaller particles of the remainder.